(CBS News) RIVERHEAD, N.Y. -- This has been a very bad summer for dolphins along the East Coast. More than 250 of them -- dead or dying -- have washed up on beaches over the past two months, and.
The first dead dolphins washed up in New Jersey and Virginia in June. Since then more have been found in Maryland and New York. Biologist Kim Durham's rescue team has recovered 27 dead dolphins.
Durham doesn't know why it's happening.
"When we were doing examinations, we would find they were very skinny animals," she says. "They were compromised animals. Some of them had skin lesions -- they were just very sick individuals."
Marine biologists believe the dolphins could be suffering from a bacterial or viral infection with symptoms that resemble measles.
"There's a lot of skin contact among them," Durham says. "They're constantly rubbing each other, so yeah, the possibility that they're spreading it among themselves is very large."
It was a virus that killed nearly 750 dolphins from New York to Florida in the late '80s. Charles Potter studied that epidemic. He's a marine mammal biologist at the Smithsonian. He believes pollution could be weakening the dolphins' immune system.
"As the animals migrate south, passing back through Virginia and are going down to the Carolinas, if this event follows what we saw in 1987, we can expect the epicenter of the epidemic to move south with the dolphins," Potter says.
"It will run its course, but there's no way to know when the end will come," Durham says.
Late Friday, another dolphin was found dead on the Jersey Shore.